In a panel van conversion I have the following 12 volt solar system:
1 off Renogy RNG-175D 175W Monocrystalline Solar Panel
1 Off Victron SmartSolar MPPT 100/15
1 off Alpha Batteries 12v 200ah Expedition Plus Agm Deep Cycle Leisure Battery (EXP12-200)
The system has worked fine until last week when the mppt failed. The mppt was showing pretty much the battery voltage and no current in good sun. When disconnected, the panel was at expected voltage.
I ordered a replacement for next day delivery and fitted it. The replacemt worked fine the afternoon it was fitted . The next morning at 8:00am the new charger was putting out 40W.
However at 9:00 am I notced the new mppt had failed
I need help to understand the why the two mppt’s have failed
Your symptoms are consistent with a poor / intermittent connection between your panel and the MPPT such as a corroded or loose MC4 connector or a failing panel. The connection is intermittent so when the MPPT tries to pull current from the panel the voltage at the MPPT drops to the battery voltage because of the high resistance. However when you test the panel with a meter you get full voltage because a meter does not draw any current. You need to fo a short circuit current test. The first check in these cases is always wiring, yhen panel, then MPPT.
Which voltage was at “pretty much the battery voltage”? The MPPTs own battery voltage or the PV voltage? What does “pretty much” mean? The battery being at 13.5V and the MPPT measuring 13.6V battery voltage is ok, but the MPPT measuring 14.2V battery would be an issue. It could mean a bad connection between battery and MPPT, a blown fuse or similar
This is a screen shot of the charger from the app.
The indicated voltage of the solar panel is similar to the battery voltage.
I am beginning to think poor connection somewhere in the cable.
Because the wiring and mppt connecttions are hard to access I am thinking of testing the mppt. Wiring up two 12 volt batteries in series on the input and a 12 volt battery on the output. I have three low capacity gel batteries I could use. What do you think?
Ok, so the PV voltage being the same as the battery voltage means that the MPPT is trying to start charging. In a working system, the PV voltage will stay at that level in the morning, until the panels actually start to produce some current, then the mode will change and the actual power point tracking will start.
This is most likely not an issue with the MPPT, but with the panels or their cabling, like pwfarnell said.
But yes, you can test the MPPT with an alternative current source in place of the PV panels.
So I have tested the mppt using three small batteries and a 21 watt bulb to make the mppt pass more current
The mppt appears to be working fine, so I need to investigate the wiring and hopefully the panel is OK
Thank you so much for your comments pwfarnell and chrigu, much appreciated
